People who believe they know a little something about a topic – confident though they may be – commonly and easily claim knowledge that is impossible for them to have, say Cornell University researchers in a newly published study in Psychological Science.The researchers catch people claiming impossible knowledge by observing when they assert familiarity with made-up concepts, fabricated events and people who do not really exist. In psychology, it’s a phenomenon called “overclaiming.”“To overclaim is to claim familiarity with – or knowledge of – something that doesn’t exist,” said Stav Atir, a Cornell graduate student in the field of psychology and lead author of a new study, “When Knowledge Knows No Bounds: Self-Perceived Expertise Predicts Claims of Impossible Knowledge.” David Dunning, Cornell professor of psychology, and Emily Rosenzweig Ph.D. ‘13, Tulane University assistant professor of marketing, are co-authors on the study.“The general idea is that practically everyone is somewhat vulnerable to overclaiming, but people are the most vulnerable in those areas of life in which they perceive themselves to be experts,” said Atir.In the first two parts of the study, the researchers showed that self-perceived financial knowledge predicts claiming an understanding of nonexistent, false financial concepts. For example, participants were provided 15 terms or concepts; a dozen were real and the rest were fabricated. Real examples included tax bracket, fixed-rate mortgage, home equity, revolving credit, vesting and stock options. The foil terms were pre-rated stocks, fixed-rate deduction and annualized credit. Ninety-three percent of participants claimed some knowledge of at least one foil.In another part of the study, despite warning participants of fictitious concepts, the researchers found that participants still overclaimed knowledge. Participants with self-perceived expertise in geography prompted assertions of familiarity with nonexistent places. Although the participants knew about Philadelphia, the National Mall in Washington and Acadia National Park in Maine, they also claimed familiarity with the brilliant blue skies of Monroe, Montana, the cheesy farmland near Lake Othello, Wisconsin and the geography of Cashmere, Oregon – all places that don’t exist.The researchers also found that 92 percent of people claimed at least some familiarity with the nonexistent biological topics of meta-toxins, bio-sexual and retroplex.Dunning said that overclaiming does not necessarily make someone a liar. “Life gives many opportunities for people to claim expertise they don’t have. Focusing research on non-existent concepts allows us to be sure they are overclaiming,” said Dunning. “Along with other researchers, we have noted that warning people that some concepts are fake does not eliminate their overclaiming, which suggests their mistaken claims are honest.”The research was supported by a Thrive Center grant and by the Templeton Foundation.